add ConnectionClosedCallback

server.go

@@ -51,6 +51,7 @@ type Server struct {
 	SessionRequestCallback        SessionRequestCallback        // callback for allowing or denying SSH sessions
 
 	ConnectionFailedCallback ConnectionFailedCallback // callback to report connection failures
+	ConnectionClosedCallback ConnectionClosedCallback // callback to report closed connections
 
 	IdleTimeout time.Duration // connection timeout when no activity, none if empty
 	MaxTimeout  time.Duration // absolute connection timeout, none if empty
@@ -317,6 +318,9 @@ func (srv *Server) HandleConn(newConn net.Conn) {
 		}
 		go handler(srv, sshConn, ch, ctx)
 	}
+	if srv.ConnectionClosedCallback != nil {
+		srv.ConnectionClosedCallback()
+	}
 }
 
 func (srv *Server) handleRequests(ctx Context, in <-chan *gossh.Request) {

server_test.go

@@ -124,3 +124,23 @@ func TestServerClose(t *testing.T) {
 		return
 	}
 }
+
+func TestServerCloseConnectionCallback(t *testing.T) {
+	connectionCloseCallbackCalled := make(chan struct{})
+	testBytes := []byte("Hello world\n")
+	_, _, cleanup := newTestSession(t, &Server{
+		Handler: func(s Session) {
+			s.Write(testBytes)
+		},
+		ConnectionClosedCallback: func() {
+			connectionCloseCallbackCalled <- struct{}{}
+		},
+	}, nil)
+	cleanup()
+
+	select {
+	case <-connectionCloseCallbackCalled:
+	case <-time.After(10 * time.Millisecond):
+		t.Fail()
+	}
+}

ssh.go

@@ -71,6 +71,9 @@ type ServerConfigCallback func(ctx Context) *gossh.ServerConfig
 // Please note: the net.Conn is likely to be closed at this point
 type ConnectionFailedCallback func(conn net.Conn, err error)
 
+// ConnectionFailedCallback is a hook for handling closed connections
+type ConnectionClosedCallback func()
+
 // Window represents the size of a PTY window.
 type Window struct {
 	Width  int